Undercarriage components for track-type work machines, such as hydraulic excavators and bulldozers, require high durability. Specifically, many of these undercarriage components come into contact with other components and move relatively thereto under the environment where sand and other hard objects intrude. It is thus necessary for the undercarriage components to have high wear resistance. To improve wear resistance, it is effective to increase the hardness of the components. Simply increasing the hardness of a component, however, will lead to reduction in toughness of the material constituting the component. The surface of the component may suffer cracking or peeling, giving rise to the need for replacement of the component. As such, in order to improve the durability of the undercarriage components of the track-type work machines, it is required to maintain high crack resistance and high peel resistance while achieving high wear resistance.
As a high-hardness and high-toughness steel capable of achieving both high hardness and high impact value, for example, a steel in which the addition amounts of alloy elements have been controlled in an attempt to achieve a Charpy impact value of at least 5 kgf·m as an index, while securing a hardness of HRC 50 or more, by tempering at a high temperature of 600° C. or higher has been proposed (see, for example, Japanese Patent Application Laid-Open No. 2003-328078 (Patent Literature 1)).